Synthesis, characterization, and photoactivity of InTaO4 and In0.9Ni0.1TaO4 thin films prepared by electron evaporation

InTaO4 and In0.9Ni0.1TaO4 thin films have been prepared by electron evaporation of successive layers of the single oxide components and posterior annealing at T 800 °C. The annealed thin films presented the monoclinic crystallographic structure typical of these mixed oxides. The electrical and optical behaviors of the films, assessed by C-V measurements, surface conductivity as a function of temperature, and UV-vis absorption spectroscopy, indicate that these oxides are wide band gap semiconductors with a variable dielectric constant depending on the annealing conditions. By reflection electron energy loss spectroscopy some electronic states have been found in the gap at an energy that is compatible with the activation energy deduced from the conductivity versus 1/T plots for these oxides. The photoactivity of these materials has been assessed by looking to the evolution of the wetting contact angle as a function of the irradiation time. All the films became superhydrophilic when irradiated with UV light, while the In0.9Ni0.1TaO4 thin films also presented a small partial decrease in wetting angle when irradiated with visible photons. © 2010 American Vacuum Society

Laser induced enhancement of dichroism in supported silver nanoparticles deposited by evaporation at glancing angles

were deposited on flat substrates by physical vapor deposition in a glancing angle configuration. The particles were characterized by scanning electron microscopy and atomic force microscopy and their optical properties examined by UV–vis absorption spectroscopy using linearly polarized light. It was found that, depending on the amount of deposited silver and the evaporation angle, part of the ‘as-prepared’ samples present NPs characterized by an anisotropic shape and a polarization dependent SPR absorption and different colors when using polarized white light at 0 and 90 . Low-power irradiation of these materials with an infrared Nd-YAG nanosecond laser in ambient conditions produced an enhancement in such dichroism. At higher powers, the dichroism was lost and the SPR bands shifted to lower wavelengths as a result of the reshaping of the silver NPs in the form of spheres. The possible factors contributing to the observed changes in dichroism are discussed

Wetting Angles on Illuminated Ta2O5 Thin Films with Controlled Nanostructure

Ta2O5 thin films with different nanostructure and surface roughness have been prepared by electron evaporation at different angles between the evaporation source and the substrates. Large variation of refraction indexes (n) from 1.40 to 1.80 were obtained by changing the geometry of evaporation and/or by annealing the evaporated films at increasing temperatures up to 1000 °C to make them crystalline. Very flat and compact thin films (n ) 2.02) were also obtained by assisting the growth by bombardment with O2 + ions of 800 eV kinetic energy. A similar correlation has been found between the wetting contact angle of water and the roughness of the films for the evaporated and evaporated + annealed samples, irrespective of their procedure of preparation and other microstructural characteristics. When the films were illuminated with UV light of h > Eg ) 4.2 eV (Eg, band gap energy of Ta2O5), their surface became superhydrophilic (contact angle < 10°) in a way quite similar to those reported for illuminated TiO2 thin films. The rate of transformation into the superhydrophilic state was smaller for the crystalline than for the amorphous films, suggesting that in Ta2O5 the size of crystal domains at the surface is an important parameter for the control of this kinetics. Changes in the water contact angle on films illuminated with visible light were also found when they were subjected to implantation with N2 + ions of 800 eV kinetic energy. The origin of this photoactivity is discussed in terms of the electronic band gap states associated with the nitrogen-implanted atoms. The possibility of preparing antireflective and self-cleaning coatings of Ta2O5 is discussed

Theoretical and experimental characterization of TiO2 thin films deposited at oblique angles

The microstructural features of amorphous TiO2 thin films grown by the electron beam physical vapour deposition technique at oblique angles have been experimentally and theoretically studied. The microstructural features of the deposited films were characterized by considering both, the column tilt angle and the increase of the column thickness with height. A Monte Carlo model of the film growth has been developed that takes into account surface shadowing, short-range interaction between the deposition species and the film surface, as well as the angular broadening of the deposition flux when arriving at the substrate. The good match between simulations and experimental results indicates the importance of these factors in the growth and microstructural development of thin films deposited at oblique angles.Ministerio de Innovación, MAT 2007-65764, CONSOLIDER INGENIO 2010-CSD2008-00023, PIE 200960I132Junta de Andalucía TEP2275, TEP5283, P07-FQM-03298, FQM-690

Nanostructured Ti thin films by magnetron sputtering at oblique angles

The growth of Ti thin films by the magnetron sputtering technique at oblique angles and at room temperature is analysed from both experimental and theoretical points of view. Unlike other materials deposited in similar conditions, the nanostructure development of the Ti layers exhibits an anomalous behaviour when varying both the angle of incidence of the deposition flux and the deposition pressure. At low pressures, a sharp transition from compact to isolated, vertically aligned, nanocolumns is obtained when the angle of incidence surpasses a critical threshold. Remarkably, this transition also occurs when solely increasing the deposition pressure under certain conditions. By the characterization of the Ti layers, the realization of fundamental experiments and the use of a simple growth model, we demonstrate that surface mobilization processes associated to a highly directed momentum distribution and the relatively high kinetic energy of sputtered atoms are responsible for this behaviourJunta de Andalucía P12-FQM- 2265Ministerio de Ciencia e Innovación CSD2008- 00023, MAT2013-42900-P, MAT2013-40852-R, MAT2014-59772-C2-1, MAT2011- 2908

Nanocolumnar growth of thin films deposited at oblique angles: Beyond the tangent rule

The growth of nanostructured physical vapor deposited thin films at oblique angles is becoming a hot topic for the development of a large variety of applications. Up to now, empirical relations, such as the so-called tangent rule, have been uncritically applied to account for the development of the nanostructure of these thin films even when they do not accurately reproduce most experimental results. In the present paper, the growth of thin films at oblique angles is analyzed under the premises of a recently proposed surface trapping mechanism. The authors demonstrate that this process mediates the effective shadowing area and determines the relation between the incident angle of the deposition flux and the tilt angle of the columnar thin film nanostructures. The analysis of experimental data for a large variety of materials obtained in our laboratory and taken from the literature supports the existence of a connection between the surface trapping efficiency and the metallic character of the deposited materials. The implications of these predictive conclusions for the development of new applications based on oblique angle deposited thin films are discussed.Junta de Andalucía P09-CTS- 5189, TEP5283, FQM-6900Ministerio de Ciencia e Innovación CSD2008-00023, MAT2010-21228, MAT2010-1844

Anisotropic in-plane conductivity and dichroic gold plasmon resonance in plasma assisted ITO thin films e-beam evaporated at oblique angles

ITO thin films have been prepared by electron beam evaporation at oblique angles (OA), directly and while assisting their growth with a downstream plasma. The films microstructure, characterized by scanning electron microscopy, atomic force microscopy and glancing incidence small angle X-ray scattering, consisted of tilted and separated nanostructures. In the plasma 2 assisted films, the tilting angle decreased and the nanocolumns became associated in the form of bundles along the direction perpendicular to the flux of evaporated material. The annealed films presented different in-depth and sheet resistivity as confirmed by scanning conductivity measurements taken for the individual nanocolumns. In addition, for the plasma assisted thin films, two different sheet resistance values were determined by measuring along the nanocolumn bundles or along the perpendicular direction. This in-plane anisotropy induces the electrochemical deposition of elongated gold nanostructures. The obtained Au-ITO composite thin films were characterized by anisotropic plasmon resonance absorption and a dichroic behavior when examined with linearly polarized light

Antibacterial Nanostructured Ti Coatings by Magnetron Sputtering: From Laboratory Scales to Industrial Reactors

Based on an already tested laboratory procedure, a new magnetron sputtering methodology to simultaneously coat two-sides of large area implants (up to ~15 cm2) with Ti nanocolumns in industrial reactors has been developed. By analyzing the required growth conditions in a laboratory setup, a new geometry and methodology have been proposed and tested in a semi-industrial scale reactor. A bone plate (DePuy Synthes) and a pseudo-rectangular bone plate extracted from a patient were coated following the new methodology, obtaining that their osteoblast proliferation efficiency and antibacterial functionality were equivalent to the coatings grown in the laboratory reactor on small areas. In particular, two kinds of experiments were performed: Analysis of bacterial adhesion and biofilm formation, and osteoblasts–bacteria competitive in vitro growth scenarios. In all these cases, the coatings show an opposite behavior toward osteoblast and bacterial proliferation, demonstrating that the proposed methodology represents a valid approach for industrial production and practical application of nanostructured titanium coatings.EU-FEDER and the MINECO-AEI 201560E055EU-FEDER and the MINECO-AEI MAT2014-59772-C2-1-PEU-FEDER and the MINECO-AEI MAT2016-75611-REU-FEDER and the MINECO-AEI MAT2016-79866-REU-FEDER and the MINECO-AEI MAT2015-69035-REDCUniversity of Seville (Spain) V and VI PPIT-USMINECO CSIC13-4E-179

Plasma Assisted Oblique Angle Deposition of Transparent and Conductive in- Plane Anisotropic ITO Thin Films

Oblique angle deposition (OAD) is a powerful technique for the fabrication of porous nanostructured oxide thin films. OAD films typically present a columnar tilted nanostructure due to geometrical shadowing effects during the thin film growth. In this work, we study the fabrication of transparent and conducting indium tin oxide films (ITO) by OAD assisted by a microwave ECR plasma. The objective of assisting the deposition with a plasma discharge is to modify the growth mechanism of the OAD process introducing additional parameters to control the columnar microstructure, composition, porosity of the films. The results indicate the OAD ITO deposition assisted by the plasma discharge is a very effective process to develop in-plane structural anisotropy in the ITO nanocolumnar films what determines their electrical properties.España MINECO-AEI MAT2016-79866-R, MAT2013-40852-R, MAT2013-42900-PEspaña MINECO-CSIC 201560E055, IJCI-2014-21226

Growth of nanocolumnar thin films on patterned substrates at oblique angles

The influence of one dimensional substrate patterns on the nanocolumnar growth of thin films deposited by magnetron sputtering at oblique angles is theoretically and experimentally studied. A well‐established growth model has been used to study the interplay between the substrate topography and the thin film morphology. A critical thickness has been defined, below which the columnar growth is modulated by the substrate topography, while for thicknesses above, the impact of substrate features is progressively lost in two stages; first columns grown on taller features take over neighboring ones, and later the film morphology evolves independently of substrate features. These results have been experimentally tested by analyzing the nanocolumnar growth of SiO2 thin films on ion‐induced patterned substrates.University of Seville: V PPIUSUniversity of Seville: VI PPIT-USEuropean Development Funds program (EU-FEDER) / Spanish Ministry of Economy and Competitiveness and Agencia Estatal de Investigación (AEI) : MAT2013-40852-REuropean Development Funds program (EU-FEDER) / Spanish Ministry of Economy and Competitiveness and Agencia Estatal de Investigación (AEI) : MAT2016- 79866-REuropean Development Funds program (EU-FEDER) / Spanish Ministry of Economy and Competitiveness and Agencia Estatal de Investigación (AEI) : MAT2015-69035-REuropean Development Funds program (EU-FEDER) / Spanish Ministry of Economy and Competitiveness and Agencia Estatal de Investigación (AEI) : MAT2015-69035-REDCEuropean Development Funds program (EU-FEDER) / Spanish Ministry of Economy and Competitiveness and Agencia Estatal de Investigación (AEI) : MAT2017-85089-C2-1- RComunidad Autónoma de Madrid S2013/MIT-3029Comunidad Autónoma de Madrid IND2017/IND766